Power tool motor with reduced electrical noise

Abstract

A power tool assembly includes a drop arm assembly rotatably supporting an arbor shaft and movable between a first drop arm position and a second drop arm position, an actuating device configured to transfer a force to the drop arm assembly when the drop arm assembly is at the first drop arm assembly position, a control system configured to control the actuating device to transfer the force to the drop arm assembly when an unsafe condition is sensed, a motor operably connected to the arbor shaft through a gear, and a gear housing which houses the gear, the gear housing formed from a non-conductive material.

The invention claimed is: 
     
       1. A power tool assembly comprising:
 a drop arm assembly rotatably supporting an arbor shaft and movable between a first drop arm position and a second drop arm position; 
 an actuator configured to apply a force to the drop arm assembly sufficient to move the drop arm assembly from the first drop arm position to the second drop arm position when the drop arm assembly is at the first drop arm assembly position; 
 a saw control unit assembly configured to control the actuator to apply the force to the drop arm assembly when an unsafe condition is sensed; 
 a motor operably connected to the arbor shaft through a gear; and 
 a gear housing which houses the gear, the gear housing formed from a non-conductive material, wherein: 
 a power shaft of the motor defines a power shaft axis; 
 a fan is mounted on a power shaft of the motor; and 
 the gear housing comprises a plurality of radial vents, the gear housing and radial vents configured to vent all air driven by the fan radially outwardly from the axis such that none of the air contacts a shaping device when the shaping device is mounted to the arbor shaft. 
 
     
     
       2. The power tool assembly of  claim 1 , wherein the gear housing extends over the fan. 
     
     
       3. The power tool assembly of  claim 1 , wherein the non-conductive material is a plastic. 
     
     
       4. The power tool assembly of  claim 1 , further comprising:
 an offset drive shaft operably connected to the power shaft through the gear and located at least partially within the gear housing; and 
 at least one first bearing rotationally supporting the offset drive shaft and located within the gear housing. 
 
     
     
       5. The power tool assembly of  claim 4 , further comprising:
 a cover plate enclosing the gear within the gear housing, the cover plate made from a non-conductive material. 
 
     
     
       6. The power tool assembly of  claim 5 , further comprising:
 at least one second bearing rotationally supporting the offset drive shaft, the at least one second bearing directly supported by the cover plate. 
 
     
     
       7. The power tool assembly of  claim 4 , wherein the offset drive shaft is operably connected to the arbor shaft through a belt. 
     
     
       8. The power tool assembly of  claim 1 , wherein the motor is further operably connected to the arbor shaft through a belt. 
     
     
       9. A power tool assembly comprising:
 a drop arm assembly rotatably supporting an arbor shaft; 
 a saw control unit assembly configured to place the drop arm assembly in a safe condition when an unsafe condition is sensed; 
 a motor including a power shaft operably connected to the arbor shaft; and 
 a housing partially enclosing the motor, the housing including a plurality of radial vents, the radial vents configured to vent air radially outwardly from an axis defined by the power shaft such that air exiting the housing does not contact a shaping device when the shaping device is mounted to the arbor shaft. 
 
     
     
       10. The housing of  claim 9 , wherein the housing is formed from a non-conductive material. 
     
     
       11. The power tool assembly of  claim 10 , wherein the housing extends over a fan mounted on the power shaft of the motor. 
     
     
       12. The power tool assembly of  claim 11 , wherein the non-conductive material is a plastic. 
     
     
       13. The power tool assembly of  claim 11 , further comprising:
 an offset drive shaft operably connected to the power shaft through a gear and located at least partially within the housing; and 
 at least one first bearing rotationally supporting the offset drive shaft and located within the housing. 
 
     
     
       14. The power tool assembly of  claim 13 , further comprising:
 a cover plate made from a non-conductive material; and 
 at least one second bearing rotationally supporting the offset drive shaft, the at least one second bearing directly supported by the cover plate. 
 
     
     
       15. The power tool assembly of  claim 14 , further comprising:
 a gear operably connected to the arbor shaft and the power shaft, the gear housed by the housing. 
 
     
     
       16. The power tool assembly of  claim 13 , wherein the offset drive shaft is operably connected to the arbor shaft through a belt. 
     
     
       17. The power tool assembly of  claim 9 , wherein the motor is further operably connected to the arbor shaft through a belt.